The present invention relates generally to wireless communication systems and, more particularly, to a system and method for adaptive equalization in a communication link in a wireless communication system.
Wireless communication devices, such as cellular telephones, are widely used as a replacement for conventional telephone systems. One advantage of the wireless communication devices is their portability. The user can operate the wireless communication device from virtually any point on earth.
One common use of wireless communication devices is in the automobile. However, the ambient noise level in an automobile can make satisfactory operation of the wireless communication device difficult or impossible. Similarly, operation in other high noise environments, such as a factory or in a crowd (e.g., at a baseball game) can also make satisfactory operation difficult or impossible.
FIG. 1 provides an illustration of a wireless communication system 2 that comprises a mobile unit 4 and one or more base station transceiver systems (BTS) 6. For the sake of simplicity, only one BTS 6 is illustrated in FIG. 1. The BTS 6 is coupled to a cell tower 8 and establishes a communication link 10 with the mobile unit 4.
As those skilled in the art can appreciate, the communication link 10 is illustrative of multiple forms of communication that occur between the mobile unit 4 and the BTS 6. For example, typical communication between the mobile unit 4 and the BTS 6 are in the form of audio communications. However, the communication link 10 is initially set up using other forms of communication that occur over a control channel. These specific steps used to establish the communication link 10 between the mobile unit 4 and the BTS 6 are known in the art and need not be described in any detail herein. Furthermore, the specific steps used to establish the communication link 10 may vary from one type of wireless system to another. For example, analog cellular communications may have one protocol used to establish the communication link 10 while digital communication devices, such as a CDMA wireless system, may have an entirely different protocol used to establish the communication link. However, the steps required by any system to establish the communication link are well known and need not be described herein.
The data transmitted from the BTS 6 to the mobile unit 4 is sometimes referred to as a forward communication link 12 while the data transmitted from the mobile unit to the BTS is referred to as a reverse communication link 14.
In a high noise environment, an audio signal transmitted on the forward link 12 can be difficult for the user to hear. Accordingly, there is a significant need for a system and method that processes the audio data received on the forward link 12 in a manner that improves intelligibility. The present invention provides this and other advantages that will be apparent from the following detailed description and accompanying figures.
The present invention is embodied in a system and method for adaptive equalization in a wireless communication system. In one embodiment, the wireless communication device transmits data to and receives data from a remote location and comprises a signal analyzer to analyze data to be transmitted to the remote location and to determine therefrom a noise characteristic present at a location of the mobile unit. The signal analyzer generates signals indicative of the noise characteristic. An equalizer is selectively activated by the generated signals to alter spectral characteristics of data received from the remote location in response to the generated signals.
In one embodiment, the signal analyzer may periodically analyze the data to be transmitted to the remote location and generate periodic signals indicative of the noise characteristic. The equalizer is an adaptive equalizer and periodically alters the spectral characteristics of the received data in response to the signals periodically generated by the signal analyzer. In one embodiment, the equalizer may be a high pass filter. The frequency response characteristic of the high pass filter may be adjusted to correspond to a frequency response characteristic of the output transducer. In some wireless devices, a plurality of different output devices may be coupled to the wireless communication device. Each external device has its own frequency response characteristic. The frequency response characteristic of the equalizer may be selected to correspond to the frequency response characteristic of the selected output transducer.